Lack of exercise: Lack of exercise can have an adverse effect on an individual's immune system. Studies say that people who are physically active have a stronger immune system.
Unhealthy diet: Unbalanced, unhealthy diet is one of the leading causes of a weak immune system among people
Excessive drinking: It goes without saying that excess alcohol causes irreparable damage to your body.
Lack of sleep: Another factor that is known to weaken your immune system to a great extent is lack or loss of sleep.
Stress: Chronic stress is known to weaken the immune system and increase an individual's chances of falling sick
Obesity: People who suffer from obesity are often known to have an extremely weak immune system.